Fox Fuel Pump Issues After Replacement/Upgrade

Ryu said:

I've got a 93 LX 5.0 that I just replaced the fuel pump (after some quick research stock OEM fuel pump should be 88 LPH) to a 155 LPH from LMR, before install everything was "fine" (and I only say fine because I'm trying to fix a different issue by replacing the fuel pump in the first place) after install while driving it hard I would lose about 60-80% of power with the accelerator pressed to the floor usually after 2k rpm for 1st gear 2.5-3k rpm for 2nd and so on. I reinstalled the old fuel pump and the issue went away so i don't believe I installed the 155 fuel pump incorrectly or pinched any fuel lines nor do i believe there was air in the fuel lines because after reinstalling the old fuel pump I had no fuel delivery issues in the first place. doing more research I saw that for a 255 LPH pump the person who did that to their 92 coup also needed to install a larger guage wire to handle the volts needed to run that pump, do i need to do something similar? what should I do from here? becasue LMR doesn't offer a stock fuel pump

This is the kit I installed https://lmr.com/item/LRS-9350A/1986-97-Mustang-155-Lph-Walbro-Fuel-Pump

TL;DR:

• my stock 1993 Mustang LX 5.0 ran normally before the fuel pump swap.
• I replaced the factory ~88 LPH pump with a 155 LPH pump from LMR.
• After the swap, the car would fall on its face under heavy throttle, losing roughly 60–80% of its power above ~2,000 RPM in 1st gear and ~2,500–3,000 RPM in higher gears.
• Reinstalling the original fuel pump immediately fixed the issue.
• Because the problem disappeared when the old pump went back in, I don't think the installation was incorrect, a fuel line was pinched, or air was trapped in the system.
• I've read that some people running 255 LPH pumps on Fox-body Mustangs upgraded the fuel pump wiring to handle the increased current draw.
• My question is whether a 155 LPH pump also requires a wiring upgrade, or if something else could be causing the power loss. or just something im missing completly

Click to expand...

Ryu said:

I've got a 93 LX 5.0 that I just replaced the fuel pump (after some quick research stock OEM fuel pump should be 88 LPH) to a 155 LPH from LMR, before install everything was "fine" (and I only say fine because I'm trying to fix a different issue by replacing the fuel pump in the first place) after install while driving it hard I would lose about 60-80% of power with the accelerator pressed to the floor usually after 2k rpm for 1st gear 2.5-3k rpm for 2nd and so on. I reinstalled the old fuel pump and the issue went away so i don't believe I installed the 155 fuel pump incorrectly or pinched any fuel lines nor do i believe there was air in the fuel lines because after reinstalling the old fuel pump I had no fuel delivery issues in the first place. doing more research I saw that for a 255 LPH pump the person who did that to their 92 coup also needed to install a larger guage wire to handle the volts needed to run that pump, do i need to do something similar? what should I do from here? becasue LMR doesn't offer a stock fuel pump

This is the kit I installed https://lmr.com/item/LRS-9350A/1986-97-Mustang-155-Lph-Walbro-Fuel-Pump

TL;DR:

• my stock 1993 Mustang LX 5.0 ran normally before the fuel pump swap.
• I replaced the factory ~88 LPH pump with a 155 LPH pump from LMR.
• After the swap, the car would fall on its face under heavy throttle, losing roughly 60–80% of its power above ~2,000 RPM in 1st gear and ~2,500–3,000 RPM in higher gears.
• Reinstalling the original fuel pump immediately fixed the issue.
• Because the problem disappeared when the old pump went back in, I don't think the installation was incorrect, a fuel line was pinched, or air was trapped in the system.
• I've read that some people running 255 LPH pumps on Fox-body Mustangs upgraded the fuel pump wiring to handle the increased current draw.
• My question is whether a 155 LPH pump also requires a wiring upgrade, or if something else could be causing the power loss. or just something im missing completly
  
  

Click to expand...

Ryu said:

Oh, I see. That's why I couldn't find it. Because it comes as a whole set and I was looking for the fuel pump as a standalone. Oh, well, I got a 155lph from rock auto. For $29, so I saved some money. And I do have that one installed, so now I just have to test it. And see if it dies again. The two Scenarios that come to mind are one. It just never dies, and I actually did fix the problem. Finally, or it does die. And I now had to figure out what the heck else is causing this issue. What do you guys suggest my next steps be besides the checklist? I know about the checklisy although I'm not very confident in my skills in being able to apply the checklist to my situation, especially if it only dies. While driving, so I would be on the road while this happens.And then I'd have to do the checklist on the side of the road so not ideal. I could get a tow or just drive around town "hoping" it dies near my home so I can tow rope it home and diagnose it there. Besides that i also have a fuel pressure regulator and fuel pressure gauge being delivered soon.So, I'll be able to test whether or not if it does die.If the problem is that the fuel pump was or still is not delivering the correct amount of pressure...

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Mustang5L5 said:

155 does not need upgraded wiring. I ran a 190 for years on stock wiring without any issues (that weren't of my own doing).

It might be in your best interest to get a fuel pressure gauge and actually monitor pressure during these events to determine if this is fuel related or other. Granted if swapping back to stock pump fixes it, it's likly a bad pump.

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